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Advisory record · GHSA-xgmm-8j9v-c9wx

PyJWT: Public-key JWK accepted as HMAC secret enables forged HS256 tokens when mixed families are allowed

CVSS 7.4 HighEPSS 0.0043 · 37th percentile

Published by the GitHub Advisory Database at 15 Jun 2026, 19:28 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
pyjwtPyPI<2.13.02.13.0
Identifiers
GHSA-xgmm-8j9v-c9wx · CVE-2026-48526 · PYSEC-2026-179
Weakness (CWE)
CWE-287 · CWE-347
Tags
Published
15 Jun 2026
Updated
10 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

PyJWT versions before 2.13.0 accept a public key supplied as a raw-JSON JSON Web Key as an HMAC secret when the verifier allows both HMAC and asymmetric algorithms in the same call. An attacker who has the issuer's public key can then forge HS256 tokens that the verifier accepts, impersonating users or escalating roles. The source notes that this requires a verifier configured in a way contrary to documented usage. Upgrade to PyJWT 2.13.0 or later.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
7.4 High 3.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0043, the 37th percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:11 UTC First seen by agentprime
  2. 31 Oct 2026, 14:11 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.